1. Field of the Invention
The present invention relates to an arrangement for positioning a transducer with respect to at least one track of a tape-shaped recording medium, whereby the transducer is displaceable perpendicular to the moving direction of the recording medium using a positioning device and an opto-electronic sensor comprises a light barrier device and a converter such that an active light beam of the light barrier is partially interrupted by an edge of the recording medium and the converter produces a control signal assigned to the interruption of the light beam to the positioning device.
2. Description of the Prior Art
Arrangements of the type generally set forth above are already known in the art. A magnetic head which contains one or more write and/or read heads is also provided as the transducer and a magnetic tape is generally provided as the tape-shaped recording medium. Such an arrangement, however, can also be employed in an optical memory in which data are recorded on a suitable, tape-shaped recording medium, for example, using a laser.
A tape-shaped recording medium, for example a magnetic tape, is usually guided between stationary guide rollers at both sides of the magnetic head in order to hold the magnetic tape in a stable position. A disruption or deviation of the magnetic tape relative to the magnetic head and perpendicular to the direction of movement of the tape often occurs as a consequence of tolerances in the manufacture of the guide rollers, as a consequence of play between the magnetic tape and the guide rollers, and as a consequence play in the seating of the guide rollers. Given high track density, i.e. given a large number of parallel tracks on the magnetic tape, this deviation of the magnetic tape can have a disruptive influence since, on the one hand, the individual write and read heads are no longer accurately positioned to the corresponding track and since, on the other hand, the number of parallel tracks and, therefore, the storage capacity of the magnetic tape becomes restrictive.
An arrangement in which a magnetic head is automatically positioned to the corresponding tracks of the magnetic tape is already known from the European published application No. 32 660. To this end, two further magnetic heads are provided, these being slightly inclined toward the magnetic tape and sensing the tracks in the proximity of the edges of the magnetic tape. The phase differences of the signals from the sensed tracks are employed to generate a signal which is supplied to a positioning device for the magnetic head and displaces the same perpendicular to the moving direction of the tape under given conditions in order to accurately position the magnetic head to the corresponding tracks. It is required, given this known arrangement, that signals are always recorded on the edge tracks. This known arrangement can no longer be employed for the positioning of a transducer in case the magnetic head comprises only a few write and read heads which can be positioned to the various tracks of the magnetic tape using the positioning device since the further magnetic heads can then no longer sense the edge tracks.
The Japanese Patent No. 55-13 25 22, fully incorporated herein by this reference, discloses an arrangement in which opto-electronic sensing arrangements, designed as light barriers, are provided in the proximity of the edges of the magnetic tape for the purpose of active positioning to the tracks of the magnetic tape. The light transmitted from a light transmitter to a light receiver is respectively partially interrupted by the magnetic tape. Dependent upon the magnitude of the interruption and, therefore, dependent upon the vertical motion of the magnetic tape, a device which varies the tension of the magnetic tape and thus compensates movements of the magnetic tape in the vertical direction is driven. This known arrangement is likewise not suitable when the magnetic head is designed so as to be displaceable to various tracks of the magnetic tape by the positioning device. Further, this known arrangement requires a relatively high expense since the apparatus for varying the pre-tension of the magnetic tape must be additionally provided.
A further arrangement for positioning a magnetic head to the tracks of the magnetic tape is known from the British published application No. 2,008,290, fully incorporated herein by this reference. This known arrangement likewise comprises two opto-electronic sensing devices disposed at the magnetic head which sense the edges of the magnetic tape. The signals output by the light receivers of the sensing arrangements are subtracted from one another and are supplied to a positioning device which respectively displaces the magnetic head in the vertical direction until the difference between the signals disappears. This known arrangement can likewise not be employed when the magnetic head is positionable to different tracks of the magnetic tape. In this case, the control signal is constant and can no longer be employed as a controlled variable for accurate positioning.